CodeForces - 375A Divisible by Seven（数学）

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <cmath>
 4 #include <algorithm>
 5 #include <cstdlib>
 6 #include <cstring>
 7 #include <queue>
 8 
 9 #define LL long long
10 
11 using namespace std;
12 
13 char s[1001000];
14 char w[1001000];
15 
16 bool mark[11];
17 
18 int main()
19 {
20 
21     memset(mark,false,sizeof(mark));
22 
23     LL top = 0,sum = 0,i,Zero = 0;
24 
25     cin>>s;
26 
27     int len = strlen(s);
28 
29     for(i = 0;i < len; ++i)
30     {
31         if((s[i] == ‘1‘ || s[i] == ‘6‘ || s[i] == ‘8‘ || s[i] == ‘9‘) && mark[s[i]-‘0‘] == false)
32         {
33             mark[s[i]-‘0‘] = true;
34         }
35         else if(s[i] == ‘0‘)
36         {
37             Zero ++;
38         }
39         else
40         {
41             w[top++] = s[i];
42         }
43     }
44 
45     for(i = 0;i < top; ++i)
46     {
47         sum *= 10;
48         sum += (w[i]-‘0‘);
49         sum %= 7;
50     }
51 
52     sum *= 10000;
53     sum %= 7;
54 
55     for(i = 0;i < top; ++i)
56     {
57         printf("%c",w[i]);
58     }
59 
60     switch(sum)
61     {
62         case 0:printf("1869");break;
63         case 6:printf("1968");break;
64         case 5:printf("1689");break;
65         case 4:printf("6198");break;
66         case 3:printf("8691");break;
67         case 2:printf("9861");break;
68         case 1:printf("8196");break;
69     }
70 
71     while(Zero--)
72     {
73         printf("0");
74     }
75     cout<<endl;
76 
77     return 0;
78 }